Drier feed distribution



K July 4, 1950 v0.1. cUMMlNGs' 2,514,204

DRI'CER FEED DISTRIBUTION Filed Jan. 50, 1946 SNN ATTORNEYS PatentedJuly 4, 195() UNITED STATES DfRIERfFI-ED DISTRIBUTION ApplicationJanuary30, 1946,.Serial.No..644,308

lGlaim. (Cl. 214-85) This ,invention relates Ato V the distribution ffine particle materials upona belt-.like conveyor and particularly tothedepositionof rubber. or synthetic rubber particles upon .acontinuous'dryer belt.

In the recent construction of manylarge plants for-,producing syntheticrubber of the soncalled GR-S type, the standardlayoutrcalled'forcontinuous .drying of the freshly coagulatedpolymerizate. The dryerdesign most favorably considered and widely usedis the horizontal'belt conveyor type in which the .wet comminuted orpelletized material is `deposited on the conveyor at one end of thedryer anddischarged at the lnpposite end. The dryer is divided intoseveral zones, .eachbeing controlled independentlyl as to draft andtemperature. `The belt passes through the various zones through smallslits in ,thebafiles which separate the zones. The belt itself is of anopen construction, usually constituted of many metal plates hingedtogether, perforated to such a degree that heated air or gasmay passthrough the same without hindrance. The materialbeing dried issupported'on the upper `side of the belt, and in order to render thistype-'of dryer eicient and practicahshould be of such texture andconsistency that air can bepassed through itreadily.

Any condition which causes lack ofuniformity inthe thickness,density,-or particle Asize of 'the layer ofgranular comminuted syntheticrubber so deposited on theconveyor--for drying, results inirregularlydried product. `The heated gas-:or air, as 'the dryingmedium, tends -tol follow'the path of `least resistance, and 'thereforeflows through the thinnest or `leastdense portions of the saidlayer. Inthe operation of these dryers, it hasoftenbeen observed thatwhenthefdr-yer conveyor carries `an unevenly distributed burden, thatVthe product includesv portions I.which-.were only partly dried while.other :portions were overheated tothe point of fusion andagglomeration.

The-condition of the vlayer depositedbnfthe dryer belt is dependent astof density, uniformity, and particle size, onthe apparatus Whichieedsthe dryer. For -example,one apparatusroften used consists of two endlesschains interconnected by and extendingcrosswise therebetween,`angle-ironlike slats of a length approximately .equal to the-width ofthe dryer belt. .This apparatus is installed-so that saidslats dip intoa hopper, pick up a load of rubber particles, and carry the particlesupward in a manner similar to a grain elevator, to a point abovetha-dryer convey.or,.where they-.unload asthey start downward. Therubberparticles are of varioussizes and. astheydisn2 charge tinto the.said, hopper; from. a @Ommmiter or. conveyor, 'theytend to,segregate.asto sizes, with the largest particles rolling to the; farthest points inthe hopper. "The, apparatus described above for, feeding the dryer 'doesnot correct the segregation which occurs intheihoppen nThe' rubberparticle layerthereafter deposited in the dryer containscoarser-particlestoward the outer edges" ofv the dryerbelt. Moreoverlthis -apparatus tends togive,a thickerand moredense condition of thelayer in `the center ofthe belt.

`Thegmoisturewin the; wet rubberparticles containsin solution anyoneofthe several coagulating materials commonly used,- such as solutions ofaluminumsulfate, sodium v chloride, barium chloride, -magnesium sulfate,sulfuric acid and hydrochloric acid. These --materials are withoutexception,A highly corrosive, and tend to cause excessive Wear oni-metalto-metal surfaces such-as in bearings andV hinges.

apparatus such asv rthe one just described contains manyfindividualparts and lis Ysubject -to frequent breakdowns and replacements.

r`It is ftherefore an object of the presentinventiorr Ytoprovideapparatusfforfor-ming layers of wet `material on 4continuousdryer conveyors, 'characterized-by great uniformity as to density,thickness, andfdistribution of particley size. ffIt 'is an object also,I'throughL the more-uniform Aheating made possible by the presentinvention, to produce fdried synthetic rubber coagulum of greateruniformity .f of physical: properties than has beenY heretofore obtained.in commercial quantities. .is afurtherobject to provide. an apparatusmechanically simple, easy to. maintain, and yrelatively* unaffected bycorrosion.

'The foregoing androther objects will.be vapparent from `theaccompanying 'speciication, when considered .fin relation to tithe f.accompanying drawing, wherein:

Fig. l-,; is; .a diagrammatic Y Y ,view ing 1-elevation showing--anlembod-iment ofthe inventionfin com- ,binationwith-v atscrewfconveyor,and a dryer belt conveyor;

Fig. 2 is a .sideview in elevation-.ofthe apparatus showninFig. y1;

- Fig. 3 illustrates: another.v embodiment of the invention, employinganalternativen means' for causingv oscillation, of a distributing chuteFig... 4 Villustrates an oscillating means, which may .be 1employed inlieu .ofoscillating .means shown in Fig. 2;

Fig. 5 isa graphical representation .oftheprinciple bywhichtheinventionA .achieves evenparticle .distributionon `the dryerconveyor;

Eig. illustrates, a. crankmeans Which-may be 3 used in lieu of the crankmeans shown in Fig. 2 and the rack and pinion apparatus shown in Fig. 3.

Referring in detail to the drawing, in which similar numerals refer tosimilar parts throughout the several views, the synthetic rubberparticles are collected in a hopper 8 as they are discharged from acomminuter or -pelletizer (not shown). The embodiment as shown in Fig. 1illustrates the use of a screw conveyor Ill to elevate the syntheticrubber particles to a spout I3.

Chutes I4 and I5, as best shown in Fig. 2, project' from a spout I3 ininverted Yarrangement. The synthetic rubber is directed into either ofthe said chutes by a butterfly damper I2 installed within the spout I3.Conveyors l@ and Il indiasiatici cate an arrangement whereby two'or'moredryer belts may be charged with wet rubber crumb from a singlecoagulating unit, only one dryer belt 24 being shown. As the rubbercrumb is directed, for example, through member I5 of the Y construction,it is charged into and carried by a screw conveyor, notshown, in housingi5 and into a communicating annular discharge chute 2I. Near the lowerextremity of chute 2l, shafts 22 and 23 are exteriorly mounted ondiametrically opposite sides of chute 2I on a horizontal axis for thepivotal support of a depending distributing chute 2E. v

Chute 2S, preferably of frustro-conicalv shape, may be supported bysuitable bearings rotatably mounted on shafts 22 and 23.v The smallerend of chute 26 projects downward and oscillates .in any desired arc of,for example, in the range of 45 to 90 degrees. The larger end of chute2E is of larger diameter than the chute 2i and in concentric andtelescopic relationship with the lower portion of chute 2|. As the chute26 swings back and forth in a predetermined arc, wetk rubberparticlesdischarged from chute 2l arel received without any possibilityof escapeby the chute 26 regardless of the-angular relationship whichvoccurs between the two chutes 2l and 25 in obtaining the arcuate path ofthe lower end of chute 26. A further reason for the larger diameter ofchute 26 is that the upper end of chute '26 is thus free topivot aboutthe lower end of chute 2l Without the sides of either of the two chutesengaging the other. l

Since it is a prime object to deposit a layer of uniformthickness uponthe dryer belt, the cycle which is executed by the lower end of chute 26is to be adjusted so that the rubber particles are deposited at aconstant rate. It is found that a highly satisfactory cycle is producedthrough the reciprocating motion obtained from a power driven doublehelical threaded transverse screw 28 in iixed position, saidreciprocating motion being transmitted to a slotted crank arm Brigidlyattached to the chute 2S. A reciprocating rod 32, which forms the`connecting element between the double helical screw 28 and the slottedcrank arm 30, is supported and limited to reciproeating motion only, byhangers'35 and 35 rigidly attached to a support 9. The length of the arcthrough which the chute rotates `is determined by the length of thehelical screw `28. The above reciprocating arrangement produces anaccurately uniform rate of deposition of rubber pary 4 and forth acrossthe said conveyor. This principle is illustrated by the geometricaldiagram shown in Fig.V 5. Referring to Fig. 5, it will be seen that lineAI is divided into several equal portions, AB, BC, etc. Line AI alsocorresponds to the path of travel of any nxed position on thereciprocating rod 32, and particularly to the pivot aixed to rod 32which rotates crank arm 3D. The reciprocating movement of pawl 3l whichis driven to and fro by the helical threaded transverse screw 28 isexactly duplicated by rod 32. Referring again to Fig. 5, the line AI isdrawn parallel to line AI. Lines drawn from the vertex O, whichcorrespond to various positions of angular displacement of the chute 26,through points A, B, C, D, E, F, G, I-I and I, denne equal intervals onthe line AI, and subtend portions on the line AI which are all equal toeach other. The line A'I' corresponds to a transverse section of thedryer conveyor belt 24. The lines drawn from the vertex O' to line A'Irepresent instantaneous positions of the longitudinal axis of thedistributing chute at regular time intervals. The trajectory of therubber particles, as they leave chute 26 at the outer extremities of itsarcuate path, tends to form a convex path downward toward the dryerconveyor 24 and thus to oiset the geometrically precise patterndescribed above. However, the distributing chute 2B is positioned justas near to the conveyor 24 as is possible, but not close enough toactually contact or otherwise disturb the layer of particles depositedby it. Therefore, the convexness of the trajectory of the particles asthey leave the chute 26 under the conditions herein set forth, is soinsignificant as to warrant no modification for any possible distortionsuch convexness might produce in the deposition principle hereindescribed.

lAlthough the embodiment described above illustrates a specificapparatus for obtaining accurately uniform deposition of particles upona conveyor passing under it at uniform velocity, it is to be noted thatother similar means may be employedto approximate the desirable resultsobtained through use of said specic embodiment of the invention. Forexample, the distributing chute 26 may be oscillated by a rack andpinion arrangement 38 as shown in Fig. 3. This latter mechanism does notgive as accurate deposition, but serves fairly well within small arcs.Again, a crank arm arrangement 42 such as shown in Fig. 6 may instead bealxed to the distributing chute to bring about particle depositionsomewhat superior to that obtained by use of the rack and pinionmechanism but not quite equal to that obtained with slotted crank arm3U. Alternative devices may be substituted for the driving portion ofthe reciprocating means, such as the one shown in Fig. 4 consisting ofan adjustable crank arm 39. The latter apparatus, substituted for thehelical threaded reversible screw 28 used in combination with a crankarm 42 aflixed to the distributing chute gives excellent results whenoperating within small arcs. It is to be understood that the drivingcrank arm 39 would preferably rotate at uniform angular velocity whilethe driven crank arm 42 oscillates in the arc through which the chute 26travels.

The frequency at which chute 26 is caused to oscillate is not criticalso long as the rate is such that the rubber particles are not given anabnormal trajectory as theyleave the chute `26, or are projected againstthe dryer conveyor in such a manner as to be bounced and scattered aboutin an unpredictable pattern. A very satisfactory range employed in thepractice of the invention is five to ten cycles per minute.

In order to obtain highly uniform layer formation, the relation of therate of oscillation of the chute 26 to the linear speed of the dryerconveyor 24 should be such as to cause considerable overlapping, say 25to 75 percent, of the successive transverse paths of particledistribution upon the dryer conveyor. In the practice of thisinvenltion, very satisfactory distribution has been obtained from thecombination of a distributor oscillation rate of six cycles per minutewith conveyor rates of one-third to one and five-eighths feet perminute. Considerable departure from these rates can be tolerated withoutappreciably affecting the uniformity of distribution.

The present invention is not restricted to any particular method orapparatus for introducing the wet rubber particles into the feeddistributor. Although the apparatus for this purpose shown is a screwconveyor, the inventor has successfully used, instead, air propulsionequipment for transporting the said particles to one or several dryers.Other arrangements and types of apparatus for delivering the rubber,particles to the feed distributor will be indicated by the specic plantlayouts.

Modications of the invention may be resorted to without departing fromthe spirit thereof or the scope of the appended claim.

What is claimed is:

In a dryer of the class described, the combination of a dryer having acontinuous belt-like conveyor upon which material to be dried iscontinuously conveyed, a pendulous chute rotatable about an axis alignedapproximately with the general direction of movement of the saidconveyor supported and suspended directly above the charge-end of thesaid conveyor, a slotted crankarm rigidly attached to the said pendulouschute extending approximately radially from the said axis of rotation ofthe chute, the said slotted portion of the crank arm being most remotefrom the said axis, a reciprocating means attached in slideable andpivoted relationship to the slotted portion of the said crank arm, meanscomprising fixed hangers for supporting and limiting the saidreciprocating means to rectilinear motion, means for producing in thesaid reciprocating means in the form of a driven double helicallythreaded screw for reciprocating rectilinear motion of uniform Velocity,a second chute in xed relation with the dryer foundation serving tosupport in pivoted relationship the said pendulous chute the diameter ofthe upper portion of the pendulous chute being sufficiently greater thanthat of the lower portion of the said second named chute as to permit onaccount of the concentric relationship between the said portions of thetwo chutes the pendulous motion of the pendulous chute, and means fordelivering to the said supporting chute a. continuous supply of Wetrubber-like particles.

ORRA J. CUMMINGS.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,741,944 Linney Dec. 31, 19291,822,313 Quiggle et al Sept. 8, 1931 1,845,839 Hoge Feb. 16, 19321,972,516 Fulmer Sept. 4, 1934 2,018,843 Folberth et al Oct. 29, 19352,100,150 Randolph Nov. 23, 1937

